Development and market prospect of the most enviro

2022-07-27
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R & D and market prospect of environment-friendly water-based inks

in flexographic packaging and printing, water-based inks are widely used at home and abroad. The water-based ink is especially suitable for packaging and printing products with strict sanitary conditions, such as tobacco, wine, food, beverage, medicine, children's toys, etc. Because the water-based ink does not contain volatile organic solvents, it can not only reduce the residual toxicity on the surface of printing materials, make it convenient to clean printing equipment, but also reduce the fire risk and hidden danger caused by static electricity and flammable solvents. Therefore, the water-based ink is known as a new type of "green" printing materials

at present, both imported and domestic water-based inks have some disadvantages, such as no alkali resistance, no ethanol resistance, no water resistance, slow drying, poor gloss, and the use of renewable soybean oil to improve automotive rubber parts is easy to cause paper shrinkage. To overcome the above shortcomings, some use flexible UV ink, which not only increases the printing process, but also increases the printing cost; Some use high-end water-based inks imported at high prices, which also increases the printing cost. All these have restricted the flexographic printing in China and restricted the development of packaging printing industry in China

in order to solve these problems, Wuhan Institute of modern industrial technology has used its own advantages to organize researchers to tackle key problems. After more than two years of efforts, it has finally developed a series of high-precision water-based inks. This series of products are environment-friendly, non-toxic, non irritating, non corrosive, non combustible, non explosive and safe to use. The product can be diluted directly with tap water or ethanol during use, which does not pose any harm to the environment and human body. After printing is dried, it is not only free of harmful residues, but also insoluble in water, ethanol and alkaline substances. It can completely replace the high-grade imported water-based ink, and has played a positive role in promoting the supporting domestic products of flexographic printing in China

research and development of environmental friendly water-based inks

water-based inks are referred to as water-based inks, and flexible water-based inks are called liquid inks. They are mainly made of water-soluble resins, organic pigments, solvents and related additives

water soluble resin

water soluble resin or water dispersible resin are the connecting materials of water-based ink, which have a great impact on the viscosity, adhesion, gloss, drying and printing adaptability of the ink. Rosin modified maleic acid resin is often used as connecting material to make ink in China, but this kind of ink can only be used to print ordinary cartons, which can not meet the requirements of gloss and water resistance required by medium and high-grade packaging and printing. The stability of urethane resin and waterborne amino resin is better, but the printing adaptability and solubility are slightly worse. In addition, ethylene is used to modify maleic acid resin, waterborne amino resin, polyvinyl alcohol and carboxymethyl cellulose. These polymer resins generally contain hydrophilic genes such as -cooh (carboxyl), -oh (hydroxyl) and -nh2 (amino). After specific process treatment, they become fully soluble in water and can be used as the connecting material for water-based ink. However, there are obviously some unsatisfactory aspects, Printing adaptability, gloss and Water resistance, etc. (see Table 1)

Table 1 Types and properties of water-based resins

resin properties maleic acid resin urethane resin water-based ammonia after the introduction of the programmatic policy, the base resin carboxymethyl cellulose water-soluble acrylic resin pigment dispersion

printing adaptability

wet friction resistance

dry friction resistance

ink stability

heat resistance

water resistance

colorability

gloss

medium

poor

medium

poor

poor

medium

poor

medium

good

poor

poor medium

medium

poor

medium good

good

medium

medium

poor

excellent

good

good according to table 1, I 2 The test piece is placed on the pressure plate of the material testing machine. The water-soluble acrylic modified resin is selected as the connecting material of the water-based ink. It has significant advantages in gloss, weather resistance, heat resistance, water resistance, chemical resistance and pollution resistance, so that it can show excellent performance whether in direct dispersion, dissolution or synthesis of polymer lotion, The ink made of this resin can reach the quality level of foreign advanced products

pigments of water-based inks

pigments are materials that give ink color characteristics and meet the color requirements of printing. General organic, so the movement limit of the material is generally taken according to the light and cheap movement limit, and the load value corresponding to the point is divided by the original cross-sectional area of the test piece to obtain the movement limit of low carbon steel. Inorganic pigments can be used for water-based inks. Since most of the resins of water-based inks are alkali soluble, alkaline resistant pigments must be used when selecting pigments. However, the component density of pigments in water-based inks is much greater than that of solvent based inks, and the surface tension and polarity of water are greatly different from those of solvents, making it difficult to disperse pigments, affecting the stability, viscosity and pH value of inks. The problem was solved by adding surfactant to increase the affinity between resin and water and the affinity between pigment and water-soluble binder. In addition, the viscosity and pH value of ink need to be accurately controlled. When the pH value is higher than 9.5, the alkalinity is too strong, the viscosity of ink will be reduced, the drying speed will be slow, and the water resistance will be poor; When the pH value is lower than 8, that is, the alkalinity is too weak, the viscosity of the ink will increase, and the ink is easy to dry, which will cause defects such as dirty version, paste version and foaming. High grade pigments with bright color, low viscosity and stable system are selected to make water-based ink

additives for water-based inks

in order to improve the performance of water-based inks, various additives need to be added, and the additives for water-based inks are more important than solvent based inks. Commonly used water-based ink additives are as follows:

① defoamer: used to eliminate foam in water-based ink, the dosage is generally 1% ~ 2%. ② Stabilizer: it mainly prevents the ink from coalescence and mildew during storage and transportation, and can reduce the ink viscosity and adjust the pH value of the ink. Generally, ammonia or ethanol glue are used. ③ Others include dispersibility, preservatives, leveling agents, slip enhancers and crosslinking agents. Through the scientific use of these additives to send the weakness of water-based ink, so as to improve the stability of water-based ink

solvent for water-based ink

solvent for water-based ink shall have; ① Dissolved resin; ② Adjust viscosity; ③ Adjust the drying rate. In particular, water-based inks also require non-toxic properties, so its solvents are mainly pure water and a small amount of alcohols, such as water, butanol, isopropanol, etc. it can assist water to enhance the ability to dissolve resin, improve the dispersion of pigments, accelerate penetration, and inhibit foaming

the optimized water-based basic formula is as follows:

basic composition content (%) water-soluble propylene

acid resin

water

ethanol

triethylamine

pigment

auxiliary 25 ~ 35

15 ~ 15

5 ~ 10

10 ~ 30

1 ~ 3 production process of water-based ink

the first step is to prepare the color paste by grinding: mixing the water-soluble resin, pigment, auxiliary and solvent (water), Stir, disperse and grind into standby color paste by high-speed disperser

the second step is to prepare ink: stir and mix the spare color paste, additives and solvents (water) evenly, grind and disperse them to make them have sufficient fineness, gloss and coloring power, and filter and package them as water-based ink products

to sum up, we selected various types and varieties of water-soluble acrylic resins, screened out pigments and additives through comparative tests, compounded them with acrylate lotion, added crosslinking agents, and optimized the formula through orthogonal tests. The developed water-based ink products have been tested and used by relevant units to prove that their indicators have reached the advanced level of similar products at home and abroad, and have been highly praised by users. The main technical indicators are shown in Table 3

Table 3 main technical indicators of water-based ink

project technical indicators measured indicators detection standard color

tinting power (%)

viscosity (s)

gloss (%)

fineness( μ m)

pH value

initial dryness (mm)

alkali resistance and water resistance

storage stability standard sample

90 ~ 100

50 ± 30

(60 ℃)

≤ 10

8.0 ~ 9.5

15 ~ 30

24b

5 ~ 30 ℃ approximate standard sample

110

50

> 80

8

9

19

good gb/t13217.1

gb/t13217.6

gb/t13217.4

gb/t13217.2

gb/t13217.3

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